An established cellular radio communication system is GSM (Global System for Mobile Communications). A further wireless communication system currently being defined is the universal mobile telecommunication system (UMTS), which is intended to provide a harmonised standard under which cellular radio communication networks and systems will provide enhanced levels of interfacing and compatibility with other types of communication systems and networks.
A fixed network interconnects wireless communication serving elements, such as Node Bs. This fixed network comprises communication lines, switches, interfaces to other communication networks and various controllers required for operating the network. Hence, a call from a UE is generally routed through the fixed network to the destination unit specific to this call. If the call is between two UEs of the same communication system the call will be routed through the fixed network to the Node B of the cell in which the other mobile station currently is. A connection is thus established between the two serving cells through the fixed network.
Wireless communication systems are distinguished over fixed communication systems, such as the public switched telephone network (PSTN), principally in that UEs move between coverage areas served by different Node B (and/or different service providers). In general, wireless subscriber units are typically provided with the ability to communicate to fixed networks such as the PSTN. If a UE wishes to call a telephone connected to the Public Switched Telephone Network (PSTN) the call is routed from the serving Node B to the interface between the cellular mobile communication system and the PSTN. It is then routed from the interface to the telephone by the PSTN.
Traditional traffic in wireless mobile cellular communication systems, such as GSM, has been circuit-switched voice data. In circuit-switched data systems, a permanent link is set up between the communicating parties, for the entire duration of the communication. Even during idle times, no other potential users may use the resources of the allocated communication path.
In addition to speech and data services, it is envisaged that, in future wireless communication systems, there will be an increasing need to support high-speed multimedia communications. A significant requirement of future wireless communication systems is their ability to provide users with improved opportunities to interact with information networks such as the Internet. It is also envisaged that the typical requirements for a subscriber communication terminal will be to transmit data at irregular intervals, in contrast to the continuous manner provided by current circuit-switched wireless communication systems. Clearly, with irregular transmissions it is inefficient to have a continuous link set up between users.
Consequently, it is envisaged that wireless communication systems will increasingly use packet-switched data technology, to interface to public data networks or information networks such as the Internet. In packet-switched data networks, information or messages are divided into standard length data packets for transmission. Each data packet is transmitted independently through the infrastructure from a source node to a destination node. This may mean that the data packets arrive out of order due to the fact that separate communication paths are established for individual data packets for the duration of the particular data packet transmission.
A cellular communication network generally interfaces with a packet-switched network, such as the Internet, via an Internet router serving as a gateway to the cellular communications network. Thus, when information is to be communicated to or from a MS or UE in a cellular communications network or system, the route is established to the appropriate Internet router, serving as the gateway of the cellular communication network. An example of a packet-based wireless communication system is the General Packet Radio Service (GPRS) developed to supplement the GSM communication system for high-speed data communication. Further details on packet data systems can be found in “Understanding data communications: from fundamentals to networking”, 2nd ed., John Wiley publishers, author Gilbert Held, 1997, ISBN 0-471-96820-X.
In a packet data based system, where a high number of subscriber units may require resources for packet transmissions at unknown and irregular intervals, it is important to optimise use the limited communication resource. Hence, a means of scheduling and ordering of the time of transmission of the individual packets is needed. This becomes even more important when individual data packets have different requirements with respect to delay, bit error rate etc.
Therefore, most packet based systems contain schedulers which control when the individual data packets are transmitted in order to share the available resource, whether time-slots in a TDMA system or power and codes in a CDMA system. An introduction to schedulers can be found in “Service discipline for guaranteed performance service in packet-switching networks”, Hui Zhang, Proceedings of the IEEE, volume 83, no. 10, October 1995.
However, known schedulers have been optimised for environments other than CDMA communication systems. For example, scheduling algorithms used for GPRS are optimised for a Time Division Multiple Access (TDMA) system and therefore not optimal for CDMA-based systems such as UMTS where codes and power must be shared.
FIG. 1 illustrates a known arrangement 100 for providing a number of clients (C1 . . . CN) 110 with access to packet data based services. The individual clients 112, 114, 116 have data packets to be transferred through a network and are competing for a time-shared resource (S) 130 such as a communication channel or CPU time. A gateway 120 is positioned between the clients and the shared resource, to co-ordinate the transferral of the data packets onto the resource. Hence, a number of data packets are “queued” until the gateway transfers the data packet to the time-shared resource (S) 130. The gateway 120 includes a gateway queue algorithm (GW) that determines how the resource is to be shared between queued data packets from the respective clients.
Two well know queue service algorithms, to allocate the communication resource between queued data packets, are:                (i) Weighted fair queuing; and        (ii) Hierarchical round robin.        